Create MNI-aligned grids in individual head-space

When combining the source-level estimates of activity in multiple subjects, the activity can first be interpolated on the individuals MRI (using ft_sourceinterpolate) and then spatially normalized to a template brain (using ft_volumenormalise).

It is also possible to define the source-reconstruction grid for each individual subject in such a way that all these grids are already aligned in MNI-space. The combination or statistic of source-level data across subjects can then directly be computed within the source-structure without the need to interpolate and normalize each volume.